Conventionally, a document such as a sheet article is usually covered with a protective film for protection because such a sheet article is readily suffered from damage. Typically, a sheet laminating apparatus is used for laminating a sheet article between two pieces of protective films in order to achieve the protective purpose.
For enhancing the laminating efficacy, the sheet laminating apparatus needs to be adjusted at a proper hot press temperature according to the thickness of the document to be laminated. In other words, a heating time period or a cooling time period is required to increase or decrease the working temperature of the sheet laminating apparatus. For example, if the working temperature of the sheet laminating apparatus is increased for laminating a thicker document, a heating time period is required. Whereas, for laminating a thinner document, a cooling time period is required to decrease the working temperature. The procedure of adjusting the working temperature of the sheet laminating apparatus is very troublesome and time-consuming.
For solving the above drawbacks, a variable-speed sheet laminating apparatus was developed. The variable-speed sheet laminating apparatus is operated at a constant working temperature but at variable hot press speeds in order to laminate documents of various thicknesses. For laminating a thinner document, the sheet laminating apparatus is operated at a faster hot press speed by adjusting a control button. Whereas, for laminating a thicker document, the hot press speed of the sheet laminating apparatus is operated at a slower hot press speed by adjusting the control button. Since an electrical controller is used to adjust the hot press speed, the conventional variable-speed sheet laminating apparatus is not cost-effective.